Using 1998 data for 8 transplantation centers located in New York City, this study found that kidney transplantation was a more cost-effective treatment than hemodialysis for the Medicare program. The initially higher costs of transplantation were fully recouped by Medicare 2 years and 10 months after surgery. For persons who are eligible for Medicare solely due to their end-stage renal disease status, transplantation would generate average monthly savings of $3800 over dialysis for the 2 years following the break-even point. For those eligible for reasons other than end-stage renal disease, for example, the aged, the average savings would be $2400. The savings difference arises because Medicare coverage for immunosuppressants for the former group ends 36 months after transplantation.